Recent findings, in the investigation of hypertension, suggest that the inception of essential hypertension occurs in the pediatric population. In the Black population, the incidence of hypertension is much greater. Familial aggregation of blood pressure (normal or elevated) suggests importance of genetic factors. These factors form the basis of the proposed research, which is directed towards: (1) Determining the incidence of hypertension in the adolescent Black population. (2) Ascertaining the pattern of familial hypertension. (3) Using quantifiable aspects of the renin-angiotensin- aldosterone system, as a system of physiologic classification, study the applicability of such measurements to the study of genetic heterogeneity of hypertension.